The limbic system: a review of its empirical foundation.

The concept of the limbic system is highly influential in many areas of the neurosciences and in their applications to clinical medicine. The value of this concept has been questioned, denied, and defended several times in the past but a comprehensive critical evaluation has never been published. In this article we take several approaches to analyse empirical data of relevance to the limbic system. First we delineate its factual application in different areas. The limbic system has a very wide scope and divergent use. Secondly we extract criteria for its definition from research literature using the bibliographic database Medline. The limbic system has been defined variously on a number of different descriptive levels from morphology to behaviour. Thirdly we review its empirical foundations comparing evidence from different sources. The limbic system lacks an adequate empirical definition in spite of numerous efforts. Last we evaluate its construction as a scientific concept from empirical facts. The limbic system is a non-empirical explanatory concept for poorly understood brain functions. We conclude that the concept of the limbic system cannot be accepted on empirical grounds. However, it is a very attractive concept in the search for explanation of brain function. The non-empirical contents of the limbic system remains largely unexplored.